Better vaccines for improved health

The immune system defends our body against infections. Vaccines help the immune system by delivering a killed or weakened microbe, or pieces of it. This way, our immune system is trained to recognise the pathogen and will remember it if it tries to infect us later on.

In the last twenty years, scientists have developed new ways of making vaccines, including using substances that improve the way the immune system responds to vaccination. These substances are known as ′adjuvants′ (meaning ′helpers′).

One of these adjuvants is called AS01. AS01 is made of small lipid droplets, containing two compounds: monophosphoryl lipid A (MPL), derived from a bacterium, and QS-21, which is isolated from tree bark. Adding AS01 to some vaccines improves their effectiveness. The EU-funded ADJSYN (Understanding how immunostimulant combinations in adjuvants synergise to enhance vaccine responses) project looked at how AS01 works.

The researchers found that AS01 worked at its best when both MPL and QS-21 were present together. They also demonstrated that in vaccinated mice AS01 was able to activate a type of immune system cell called Natural Killer Cells (NKC). This helps the immune system to remember the microbe that is targeted by the vaccine. The activation of NKC was very fast, as it started 4h after vaccination.

By revealing what happens early after vaccination, ADJSYN’s results will be useful for clinicians wanting to develop safe and efficient vaccines against complex diseases. Already, vaccines against malaria, tuberculosis and shingles adjuvanted with the combination of MPL-and QS-21 are undergoing advanced clinical tests.